1. Field of the Invention
The present invention relates to a photographic printer and a film scanner. More particularly, the present invention relates to a photographic printer and a film scanner of which a light source is simplified and also illumination can be controlled with high precision.
2. Description Related to the Prior Art
A photographic printer incorporates a light source. A conventional light source for printing is a halogen lamp. Three-color filters, called light-adjusting filters or cut filters, are inserted into a printing light path, to adjust light amounts and spectral distribution of the printing light. Instead of the halogen lamp, JP-A (Japanese Patent Laid-open Publication No.) 57-179832 discloses a light source for a color printer inclusive of monochromatic cathode-ray tubes (CRTs) emitting Red, Green and Blue light. The illuminating brightness is changed to adjust the light amounts and light spectral distribution.
In the light source with a halogen lamp, light-adjusting filters or cut filters must be inserted in the printing light path, and are shifted by a shifter device which is inevitably incorporated in the printer. The shifter device requires precision, high speed and durability for the purpose of printing exposure with high precision, and conventionally has complexity in construction. There is a further problem in the use of the three adjusting filters, which have unwanted absorption between the filters, to make it complex to calculate set positions of filters. The halogen lamp also emits infrared rays or ultraviolet rays unnecessary for exposure. There is a problem in that additional filters are required also for eliminating the infrared rays or ultraviolet rays. Another problem is low efficiency in conversion of printing light. A lamp spending electric power of hundreds of watts is required. Capacity of a power source must be enlarged, to result in a disadvantage in structural design. When in use of the three CRTs for the Red, Green and Blue light disclosed in JP-A (Japanese Patent Laid-open Publication No.) 57-179832, even the change in the illuminating brightness inevitably enlarges and complicates the construction of the printer.
The photographic printer includes the filters, a printing lens, a black shutter, and other various optical elements. Each optical element may have characteristics varied between portions of the optical element. Unevenness in density or colors may take place on a print produced by way of the optical element. For example, the printing lens has such a characteristic that an amount of light transmitted through a peripheral portion is relatively small, to cause unevenness in density or colors. It would be possible to correct the unevenness by use of an additional optical element having a characteristic reverse to the uneven pattern, such as a parabola filter or a color filter. However the uneven pattern of the printing lens varies with the change in magnification at which the printing lens is set. In the printer of which the printing magnification is variable, plural filters are required in association with different magnifications. However it is actually difficult to practice the printer provided with the plural filters for eliminating unevenness.